The signs of the present perfect tense are already, yet, before, and just.

The perfect tense is divided into two parts: one is the auxiliary verb, and the other is the past participle of the substantive verb -ed. Specifically, the auxiliary verb have is used to express "time" to indicate whether the action occurred in the past, present or future; the past participle is used to express the "state" of the action to indicate that the action has been completed.

It is composed of: subject, auxiliary verb (have/has), past participle of the verb. (have/has done)

Extended information:

Basic structure: subject have/has past participle of verb (p.p)

1. Affirmative sentence: subject have/has past participle of verb (p.p) (V-ed) object (or other).

2. Negative sentence: subject have not/has not past participle of verb (p.p) (V-ed) ) object.

3. General questions: Have/Has past participle of subject verb (p.p) (V-ed) object (or other)?

Affirmative answer: Yes, I /they/we/you have. Or Yes, she/he/人名has.

Negative answer: No, I/they/we/you haven't. Or No, she/he/人名hasn 't.

4. Special interrogative sentences: special interrogative words, general interrogative sentences (have/has, subject, past participle, other)